Provide image for each instrument + update images + delete not needed images in /docs/images/

[mariobehling]

Please do the following:

1. Delete all no longer needed/outdated images.
2. Provide an image with actual measurements for each instrument in a) in high resolution and b) in web resolution
3. Update instrument images to the latest version.
4. Add all images to the gallery in the Readme.md file

[CloudyPadmal]

Duplicate of #1476